Kim Kardashian's step-father Bruce Jenner is consulting a divorce lawyer, it has been claimed.

The former US Olympian has been married to Kardashian-Jenner matriarch Kris Jenner for 21 years.

The couple's ups and downs have been well-documented on the family's hit US reality show Keeping Up with the Kardashians.

According to the National Enquirer, Bruce Jenner has hit a breaking point with the domineering momager.

"Bruce feels that Kris treats him like a doormat, and he's had enough," a source told the publication, adding, "She constantly belittles his appearance and complains to mutual friends that he's a boring old fart."

An insider claims Bruce has been helped by sports entertainment lawyer friend on evaluating his assets.

The couple is estimated to share a US$155 million fortune.

"He's also talked to a divorce attorney buddy about potential custody arrangements for his two girls with Kris," the source claimed.

Bruce and Kris married in 1991. The couple share teenage daughters Kendall and Kylie and he is step-father to Kourtney, Kim, Khloe and Rob Kardashian from her previous marriage to late attorney Robert Kardashian.